Pedicle screw placement accuracy using ultra-low radiation imaging with image enhancement versus conventional fluoroscopy in minimally invasive transforaminal lumbar interbody fusion: an internally randomized controlled trial

OBJECTIVE A previous study found that ultra-low radiation imaging (ULRI) with image enhancement significantly decreases radiation exposure by roughly 75% for both the patient and operating room personnel during minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) (p < 0.001). However, no clinical data exist on whether this imaging modality negatively impacts patient outcomes. Thus, the goal of this randomized controlled trial was to assess pedicle screw placement accuracy with ULRI with image enhancement compared with conventional, standard-dose fluoroscopy for patients undergoing single-level MIS-TLIF. METHODS An institutional review board-approved, prospective internally randomized controlled trial was performed to compare breach rates for pedicle screw placement performed using ULRI with image enhancement versus conventional fluoroscopy. For cannulation and pedicle screw placement, surgery on 1 side (left vs right) was randomly assigned to be performed under ULRI. Screws on the opposite side were placed under conventional fluoroscopy, thereby allowing each patient to serve as his/her own control. In addition to standard intraoperative images to check screw placement, each patient underwent postoperative CT. Three experienced neurosurgeons independently analyzed the images and were blinded as to which imaging modality was used to assist with each screw placement. Screw placement was analyzed for pedicle breach (lateral vs medial and Grade 0 [< 2.0 mm], Grade 1 [2.0-4.0 mm], or Grade 2 [> 4.0 mm]), appropriate screw depth (50%-75% of the vertebral body's anteroposterior dimension), and appropriate screw angle (within 10° of the pedicle angle). The effective breach rate was calculated as the percentage of screws evaluated as breached > 2.0 mm medially or postoperatively symptomatic. RESULTS Twenty-three consecutive patients underwent single-level MIS-TLIF, and their sides were randomly assigned to receive ULRI. No patient had immediate postoperative complications (e.g., neurological decline, need for hardware repositioning). On CT confirmation, 4 screws that had K-wire placement and cannulation under ULRI and screw placement under conventional fluoroscopy showed deviations. There were 2 breaches that deviated medially but both were Grade 0 (< 2.0 mm). Similarly, 2 breaches occurred that were Grade 1 (> 2.0 mm) but both deviated laterally. Therefore, the effective breach rate (breach > 2.0 mm deviated medially) was unchanged in both imaging groups (0% using either ULRI or conventional fluoroscopy; p = 1.00). CONCLUSIONS ULRI with image enhancement does not compromise accuracy during pedicle screw placement compared with conventional fluoroscopy while it significantly decreases radiation exposure to both the patient and operating room personnel.